Conventional process systems used in the production of microelectronic devices usually include a process module that utilizes a transfer chamber or loadlock module to align and/or center a semiconductor wafer to improve and/or monitor the accuracy of film processing. The process module is used for the purpose of intentionally growing and/or depositing layers of film onto a semiconductor wafer. Each step in the process system requires interfacing between modules to ensure quality of the microelectronic device and provides an opportunity for an oxide layer to form or re-form on the wafer.
The presence of an oxide layer with an unknown composition usually affects both electrical as well as physical properties of the film being deposited or grown, reducing the quality of the microelectronic device. For example, these layers may inhibit good contact with a silicon (Si) substrate, leading to poor epitaxial Si growth. They may also reduce a resultant dielectric quality, resulting in lower capacitance and current leakage in the microelectronic device. In polysilicon films, these layers may result in higher resistance than expected, thus affecting the operation of the microelectronic circuit. Furthermore, the layers may reduce the uniformity of film layers as well as undesirably increase the final thickness of the microelectronic device.
One approach to the oxide removal problem includes the use of high temperature processing within the processing module. For example, the surface of a wafer may be etched using a hydrogen anneal or baking process at a high temperature. However, this process requires the use of high temperatures and typically results in a non-uniform surface and/or potential damage to the wafer. Moreover, each of these processes requires either separate equipment or an additional step in processing. This additional step undesirably introduces an opportunity for further oxidation to occur.
Because hardware such as stainless steel or quartz within either a high quality thermal process or transfer chamber module are incompatible with any gas or etch process, approaches to the oxide removal problem typically include use of a separate oxide layer removal module. For example, a separate wet etch module may be used to remove an oxide layer from a wafer by immersing the wafer into a solution, such as hydrofluoric acid (HF). However, this type of processing is difficult to control and typically produces an undesirably uneven wafer surface. Other approaches may utilize a separate module for coating either a single wafer or a batch of wafers with a vaporous solution. However, each of these approaches undesirably introduces an additional step or interface into the process system. Therefore, it is desirable to ensure the effective removal of interfacial oxides without introducing unnecessary steps into the processing of semiconductor wafers.